Poppy and Branch discover that they are but one of six different Troll tribes scattered over six different lands devoted to six different kinds of music: Funk, Country, Techno, Classical, …
Poppy and Branch learn that there are other Troll lands made up of other types of music. They live on the Pop Troll Island, while the others are Rock, Classical, Funk, Country, and Techno. Queen Barb of the Rock Trolls wants to collect the six strings from every Troll clan to make sure only rock music prevails. Poppy, Branch, and Biggie set off on an adventure to stop Barb from destroying other kinds of music. Meanwhile, Cooper sets off on his own journey after learning that there are other giraffe Trolls like him.
Poppy and her friends team up with a Country Troll named Hickory to stop Barb. They are found by the Funk Trolls, who are actually Cooper’s real family. They reveal that it was the Pop Trolls who tried to claim all the music for themselves, forcing the other Troll leaders to take their strings and flee. Barb captures the Funk Trolls, and Poppy and Branch split up after he tells her that she won’t listen to anyone who tries to tell her not to keep going. Hickory then turns out to be part of a Yodeler duo of Trolls who were sent by Barb to get Poppy’s string. She then shows up and captures Poppy after succeeding in getting the other Trolls and their strings.
Barb puts on a rock show where she unites the strings to create the Ultimate Power Chord. Branch and the other Pop Trolls come to help Poppy, but Barb turns him and the other Troll leaders into Rock Zombies. She nearly does the same to Poppy, but she fakes it by covering her ears with gumdrops, and then destroys Barb’s guitar, and also the strings. All the Trolls then create a unique sound with their own individual beats and rhythms. Barb joins in as well, and the Trolls all make peace.
The Trolls accept that their differences make them unique.
A celebration of the Techno Trolls is crashed by the Rock Trolls, led by Queen Barb. After Barb destroys his DJ station with her guitar’s power, King Trollex is forced to surrender the blue string that powers Techno music.
Poppy, still adjusting to her new role as queen, receives a message from Barb that invites all Trolls to a party to unite their music. Her father, King Peppy tells the story of how the Troll tribes became scattered throughout their world Troll Kingdom. The six primary tribes each represented by a different style of music: Pop, Funk, Classical, Techno, Country, and Rock. The music is powered by a magical string kept by the leader of each tribe. Having separated their tribes following discord and disagreement over which style of music was the best, Poppy wants to help Barb unite the different forms of music, but both her father and Branch warn her not to trust Queen Barb’s intentions and to accept that the other Trolls are different. Poppy refuses to listen, sending a cheerful reply to Barb via Debbie, Barb’s pet bat.
Meanwhile, Barb gloats over her victory of snatching the Techno string, revealing her plan to string an enchanted guitar with all six strings, and play a power chord strong enough to destroy all other music, replacing it with rock.
Wanting to prove herself as a good queen, Poppy travels via air balloon to recruit the other groups of Trolls, Branch joining her in an attempt to express his feelings towards her. Biggie accidentally stows aboard the balloon, having being tempted by cotton candy, and joins them. Meanwhile, Cooper, who feels like the black sheep among the Pop trolls, goes on a journey himself after realizing one of the Troll Tribes looks just like him. He goes into a forest coming upon a herd of monsters, who he thought were trolls like him. He escapes but ends up lost in a desert. He tries to drink from a mirage, but snaps out of it and is abducted by a spaceship wielding magical soap bubbles.
The balloon ends up in the land of Classical Trolls, which, to Poppy’s horror, is in ruins. A single small flute named Pennywhistle tells Poppy their town had been decimated by Barb’s armada, who captured all the citizens and stole the yellow Classical string. Poppy decides to unite the other Trolls to stop Barb. Branch and Biggie urge her to return home to protect the pink Pop string, but Poppy reveals it hidden in her hair. They then travel to the Country Trolls’ land, but after introducing themselves with a loud medley of pop songs, are jailed by an offended Delta Dawn, leader of the Country Trolls.
While in jail, a Country Troll named Hickory, claiming to be moved by Poppy’s motives, busts them out, leading to a chase to a ravine. The group flies halfway over the ravine, only to be hanging suspended for just a second, before falling into a river. Branch does not trust Hickory, even when Hickory builds a raft to take the group downstream. The conversation is interrupted by Chaz, a Smooth Jazz Troll hired as a bounty hunter to catch Poppy for Queen Barb, whose music causes Poppy and Branch to fall into a deep hallucination. Hickory incapacitates Chaz, but Biggie decides to return home, declaring that Poppy had broken their previous pinky promise and led them all to danger. Shortly after, the group is abducted by the spaceship that snatched Cooper.
Inside the spaceship, the group discovers the Funk Trolls, and meets up with Cooper, who is revealed to have been the long-lost identical twin of the Funk Troll prince, Prince D. His egg was snatched out of the nest when he and his twin were babies. His parents, King Quincy and Queen Essence, couldn’t find him so the Pop Trolls raised him as one of their own. Cooper then tells Poppy he finds comfort in identifying with both Pop and Funk. Quincy and Essence also reveal to Poppy that long ago the original Pop Trolls had attempted to steal the strings and remix the other five music styles into Pop, forcing the other Trolls to each take one string and divide their tribes to save their music. Quincy explains to Poppy that differences are not bad, and trying to make all Trolls the same does not help the problem.
After the Rock Trolls hijack the Funk Trolls’ ship to steal the purple Funk String, Cooper ejects the group in bubbles, accidentally separating Hickory from the two. Poppy refuses to return home to their friends, and Branch admonishes her insisting she cannot be a good queen if she is a poor listener, but with his head clouded full of anger, sadness, frustration, confusion, fear, and loss of hope, Branch, in despair, questions their friendship, and the two go their separate ways. Branch is soon captured by both K-Pop and Reggaeton bounty hunters. However, he convinces them to stop capturing and fighting and save Poppy and all music.
Poppy reunites with Hickory, showing him the Pop string. Hickory urges her to return home, but suddenly is revealed to have been a Yodel Troll all along. He and another Yodel Troll, Dickory, who had been hiding within Hickory’s back legs, had been hired to capture her for Barb, but Hickory had a change of heart. Before she can escape, Poppy is then captured personally by Barb, who takes possession of the sixth and final string. Biggie returns home and after seeing it in shambles, feels remorse over abandoning Poppy. He gathers together their remaining friends to go rescue her and Branch, entering the land of the Rock Trolls.
Barb has Poppy imprisoned over a large concert stage where all the captured Trolls are the audience, and admits she empathizes with Poppy’s attempts to be a good queen, as she is trying to make rock supreme to prove her own leadership. Barb uses her enchanted guitar to turn Branch and the leaders of the other lands into rock zombies. Poppy seemingly is transformed into a rock zombie when she falls onto the stage, but upon grabbing Barb’s guitar, is revealed to have been wearing gumdrop earplugs. She admonishes Barb for being a poor queen by not taking time to listen to her people, and smashes the guitar. While it snaps the possessed trolls out of their rock zombie state, it destroys the strings, ergo stopping the flow of music, taking the trolls’ colors with it.
Cooper hears his heartbeat over a microphone, and creates a rhythmic beat with it, other trolls joining in with clapping, stomping, and other forms of soundmaking, reviving the power of their music, and Poppy encourages everyone to sing together as their colors are restored. Realizing how important other forms of music are, and encouraged by her father Thrash, the repented Barb joins in, regaining her colors, and eagerly accepts Poppy’s offer of friendship.
Branch is finally able to profess his love to Poppy who reciprocates his feelings, and everyone performs together, all Trolls finally reunited while celebrating their differences.
In a mid-credits scene, Bridget and King Gristle arrive to the Pop Troll village, unaware of the events that have taken place, and worried they have missed the party.
The film starts with Cloud Guy (Walt Dohrn) recapping how Poppy (Anna Kendrick) and Branch (Justin Timberlake) saved their world. What they don’t know yet is that there are other Troll islands besides theirs. We cut to the land of Techno Trolls, where King Trollex (Anthony Ramos) is leading a party to “One More Time”. The celebration is interrupted by the arrival of the Rock Trolls, led by Queen Barb (Rachel Bloom). She demands the string of the Techno Trolls, and when Trollex refuses to give it up, Barb plays a powerful rendition of “Rock You Like a Hurricane”, bringing destruction to the land. Trollex has no choice and gives up the string before she kidnaps him and the rest of the trolls.
On the Pop Troll island, Poppy is still having fun with her friends. Branch is struggling to tell Poppy how he really feels about her. The group gathers when Guy Diamond (Kunal Nayyar) is about to have a baby. He gives birth to Tiny Diamond (Kenan Thompson), who raps his introduction. After a whole song-and-dance session, a Rock Troll bat creature flies in with a message from Barb to Poppy, saying she would like her to bring her string for her Rock World Tour. King Peppy (also Walt Dohrn) panics and tries to cover things up until he’s forced to reveal to Poppy and the other Trolls that there are other Troll Islands. Long ago, the Troll ancestors came up with six different music groups – Pop, Rock, Techno, Classical, Funk, and Country. While they were all united, the Trolls started growing intolerant of each other’s music before the leaders of each group decided to take their strings and go their separate ways. Peppy and Branch are ready to hide all the other Trolls, but Poppy wants to take a chance and meet with Barb, despite the protests of the others.
That night, Poppy sneaks out to go on her journey on a hot air balloon, when she is caught by Branch. Although she appears set to go off on her own, Branch reluctantly joins her. Meanwhile, Cooper (Ron Funches) sees the book of the Troll ancestors and sees that one of them is a giraffe Troll like him. He sets off on his own to find his true family.
Barb returns to Rock Troll Island where she has a second string to add to her powerful guitar, with which she will use to unite the whole world…under ROCK. Her father is King Thrash (Ozzy Osbourne), who isn’t all quite there, but is still a firm believer in the power of rock.
On their ride over, Poppy and Branch find that Biggie (James Corden) and Mr. Dinkles (Kevin Michael Richardson) have stowed away after eating all the cotton candy that Poppy was saving for Barb. They arrive on the Classical Troll Island town of Symphonyville, which has been devastated by Barb and the Rock Trolls. The group finds Pennywhistle (Charlyne Yi), who tells Poppy that Barb came and overwhelmed their leader, Trollzart (Gustavo Dudamel), dismissing classical music as boring before stealing the Classical string and kidnapping Trollzart and the Classical Trolls. Poppy realizes Barb’s true intentions and decides she has to save the other Trolls before Barb destroys their world. Although Branch wants to go back, Poppy insists on continuing the journey, even having brought the Pop string with her. She pinky-promises Biggie that she will protect them, and a pinky promise for Trolls is powerful enough to send waves across the land. Pennywhistle stays behind the help rebuild the land.
Barb receives Poppy’s cute invitation (with glitter) to join forces and become best friends, which she takes as an insult. She decides to send out four sets of bounty hunters to go after her – Chaz, the Smooth Jazz Troll (Jamie Dornan), the Reggaeton Trolls led by Tresillo (J Balvin), the K-Pop gang (Red Velvet), and the Yodelers (who are absent). Barb promises them that if they capture Poppy, she will let them keep their own music on a small piece of land.
Poppy, Branch, and Biggie (and Mr. Dinkles) make it to the Country Troll Land town of Lonesome Flats, led by Delta Dawn (Kelly Clarkson). The Country Trolls sing a gloomy song, which Branch likes but Poppy thinks it means that they need to introduce them to the music they love. They do a medley of feel-good songs (“Wannabe,” “Who Let The Dogs Out,” “Gangnam Style”, and “Party Rock Anthem”), only to get thrown in jail. Delta tells them that they know about Barb and they are fine sticking to their own music without interference. As Branch starts to dig them out, they are freed by another Country Troll named Hickory (Sam Rockwell). He leads them on an escape, but Delta chases after them with her group before the heroes end up falling off a cliff into a river.
Hickory builds the group a raft to keep them going. Branch tells Poppy he doesn’t trust Hickory, but she thinks it just means he doesn’t trust her. They are then found by Chaz, who uses his Smooth Jazz powers to put Poppy, Branch, and Biggie in a trance. However, Hickory manages to block it out by putting gumdrops in his ears and then kicks Chaz into the river. Biggie freaks out and gets mad at Poppy for not being able to protect them, and he rides Mr. Dinkles back to the Pop Troll Island.
Cooper continues on his own journey, but he has been traveling for so long that he has started to hallucinate. Just when it looks like he’s ready to give up, an aircraft arrives and pulls him up inside.
The aircraft then finds Poppy, Branch, and Hickory, bringing them inside. It belongs to the Funk Trolls, where it is revealed that Cooper is a prince who was separated from his family when he was just an egg. His parents are King Quincy (George Clinton) and Queen Essence (Mary J. Blige), and his twin brother is Prince D (Anderson .Paak). When Poppy asks Quincy and Essence for their help in stopping Barb, they decline. Prince D tells Poppy through song the truth about what happened with the strings – it was the Pop Trolls who tried to take all the strings and tried to claim all of music as their own by remixing other types of music. The other Troll leaders grabbed their own strings and fled. Poppy tries to argue that differences in music and taste don’t matter, but the others think denying their differences means denying who they are. The Rock Trolls then start to attack, so the Funk Trolls try to fight back. Poppy, Branch, and Hickory are then ejected from the ship as Barb and her minions take over.
Poppy and Branch then argue as she is insistent on trying to continue the journey, but Branch tells her that she has been ignoring everyone who has been trying to tell her not to pursue this any further, and that a good queen would listen. Branch then goes off on his own, leaving Poppy behind. This leads them to sing on their own “Perfect For Me” as they quickly miss each other. Branch is then found by both the K-Pop Gang and the Reggaeton Trolls, who engage in a dance-off. Branch then convinces them that they don’t need to let Barb decide which music gets to be saved, and they decide to listen to him.
Poppy is found by Hickory, who reveals himself to have a partner, Dickory (Flula Borg). They are actually the Yodeler bounty hunters sent by Barb to get Poppy’s string, but Hickory actually feels bad about it. Barb then finds them and gets her hands on the string, now finally completing her mission.
Biggie and Mr. Dinkles return to their home, only to find that the Rock Trolls got there first. Guy, Tiny, Satin and Chenille (Caroline Hjelt and Aino Jawo), Smidge (also Walt Dohrn), and Legsly (Ester Dean) come out of hiding. Biggie feels bad for abandoning Poppy and resolves to round up his friends to go rescue her by using Rock Trolls disguises.
Barb keeps Poppy as a prisoner and reveals the pressure she feels to be a queen that everyone can follow, which Poppy can relate to. Her friends manage to sneak in as Barb’s back-up players. She presents the captured Troll leaders to the whole Rock Troll audience. Barb starts to perform “Barracuda” as she gets all the strings together to create the Ultimate Power Chord. Before she can unleash its true power, Branch and the other bounty hunters show up. Barb almost zaps Poppy with the Power Chord’s…power, before Branch jumps in and gets hit by it and turns into a Rock Zombie. She does the same to Trollex, Delta, Trollzart, Quincy and Essence before trying to hit Poppy with the Chord. She appears to become a Rock Zombie, and Barb tosses her the guitar to play rock until she reveals that she covered her ears with gumdrops. Poppy smashes the guitar, which destroys the strings and saps all the Trolls of their color. Barb blames Poppy for destroying all music, but Cooper grabs the mic and plays the music beating from within him. All the other Trolls from every clan start to join in, creating their own rhythm for the song “Just Sing”. Even Barb joins in, and all the Trolls make peace with the fact that they share different tunes. Poppy and Branch then express their love for one another.
Poppy and Branch later tell all the Troll children the new history of all Trolls and how they can appreciate each other’s differences.
Midway through the credits, the Bergens King Gristle (Christopher Mintz-Plasse) and Bridget (Zooey Deschanel) arrive too late and realize they missed the whole party.